The principle of HVDC transmission is high-power long-distance DC transmission, which takes advantage of DC stability and has no inductive reactance, capacitive reactance and synchronization problems.

The transmission process is DC. It is often used for submarine cable transmission and communication between asynchronous AC systems.

HVDC transmission technology is used for long-distance transmission of electric energy through overhead lines and submarine cables. At the same time, it is also used to connect independent power systems in some occasions that are not suitable for traditional AC connection. The world's first commercial HVDC transmission line 1954 was born in Sweden, connecting Sweden and Gotland Island.